Database recovery apparatus and method

Abstract

A method, system and program for efficiently archiving and recovering a database is disclosed. The archiving process utilizes a reverse chronological order for the tape to facilitate efficient restoration of the database. The recovery processing utilizes a linked list to track record updates and avoid updating the same record with anything but the most current information.

Having thus described our invention, what we claim as new, and desire to secure by Letters Patent is: 
     
       1. A method for recovering a database with one or more records to a previous state at a particular time, comprising the steps of: (a) archiving one or more changed records in the database since said particular time, said one or more changed records archived in reverse chronological order, wherein said step of archiving one or more changed records further comprises the steps of: sorting said one or more changed records in said reverse chronological order; and   archiving said sorted one or more changed records onto a tape storage device in said reverse chronological order; and;     (b) recovering the database by applying the one or more changed records archived in said tape storage device in said reverse chronological order so that only the archived changed record occuring nearest in time to said particular time is applied to said database.   
     
     
       2. A method as recited in claim 1, wherein the database is relational. 
     
     
       3. A method as recited in claim 1, including the step of storing the database on a disk. 
     
     
       4. The method as recited in claim 1, wherein said step of archiving one or more changed records in the database since said particular time further comprises the step of storing said one or more changed records in a direct access storage device; wherein said step of sorting said one or more changed records further comprises the steps of: creating a two column array in said direct access storage device, wherein each row of said two column array corresponds to one of said one or more changed records stored in said direct access storage device, wherein a particular row contains an address and a length of a particular corresponding changed record; and   organizing said created two column array into said reverse chronological order,     wherein said step of archiving said sorted one or more changed records onto said tape storage device further comprises the step of: transferring said one or more changed records from said direct access storage device to said tape storage device in accordance with said created two column array organized in said reverse chronological order.     
     
     
       5. An apparatus for recovering a database with one or more records to a previous state at a particular time, comprising: (a) means for archiving one or more changed records in the database since said particular time, said one or more changed records archived in reverse chronological order, wherein said means for archiving one or more changed records further comprises: means for sorting said one or more changed records in said reverse chronological order; and   means for archiving said sorted one or more changed records onto a tape storage device in said reverse chronological order; and     (b) means for recovering the database by applying the one or more changed records archived in said tape storage device in said reverse chronological order so that only the archived changed record occurring nearest in time to said particular time is applied to said database.   
     
     
       6. An apparatus as recited in claim 5, wherein the database is relational. 
     
     
       7. An apparatus as recited in claim 5, including a disk for storing the database. 
     
     
       8. An apparatus as recited in claim 5, including a computer to recover the database by applying the archived one or more changed records in the database since said particular time so that only the archived changed record occurring nearest in time to said particular time as applied to said particular record in said database. 
     
     
       9. The apparatus as recited in claim 5, wherein said means for archiving one or more changed records in the database since said particular time further comprises a means for storing said one or more changed records in a direct access storage device, wherein said means for sorting said one or more changed records further comprises: means for creating a two column array in said direct access storage device, wherein each row of said two column array corresponds to one of said one or more changed records stored in said direct access storage device, wherein a particular row contains an address and a length of a particular corresponding changed record; and   means for organizing said created two column array into said reverse chronological order,     wherein said means for archiving said sorted one or more changed records onto said tape storage device further comprises: means for transferring said one or more changed records from said direct access storage device to said tape storage device in accordance with said created two column array organized in said reverse chronological order.